Short answers, pulled from the story.
The central plot device in Street Fighter X Tekken is a cube-shaped artifact named Pandora that crash-landed in Antarctica. This object releases a water-like energy that empowers combatants whenever they fight near it.
Street Fighter X Tekken features 38 playable characters with 19 fighters from each franchise. Players can utilize a six-button system for Street Fighter characters and a four-button system for Tekken characters.
Street Fighter X Tekken was released in 2012 as a crossover fighting game published by Capcom. The development process involved Capcom and Dimps for console versions and QLOC for the PC port.
Yoshinori Ono and Katsuhiro Harada produced Street Fighter X Tekken. Ono served as the producer of Street Fighter IV while Harada produced Tekken.
Street Fighter X Tekken faced controversy because Capcom included characters on the game disc that required additional payment to unlock. Critics also noted that online tag-team matches were unavailable for the Xbox 360 version despite being advertised.